Finding the max value of an attribute in an array of objects in an object

Question

I have a JavaScript object and want to get the highest value of all entries. I have tried this:

d = {
"A": [ {"value": 10}, {"value": 20}, {"value": 30} ],
"B": [ {"value": 50}, {"value": 60}, {"value": 1000} ],
}

Object.keys(d).map(
    function(k) { 
        Math.max.apply(Math, d[k].map(
            function(e) {
                console.log(value);
            }
        ))
    }
)

The result should be 1000.

I have some JSON data no you don't you have a javascript object, JSON is a different thing — Liam
– Liam, Commented Jun 18, 2019 at 7:56

Nenad Vracar · Accepted Answer · 2019-06-18 07:56:56Z

7

You can use spread syntax ... in Math.max after you map and flatten the array.

const d = {
  "A": [ {"value": 10}, {"value": 20}, {"value": 30} ],
  "B": [ {"value": 50}, {"value": 60}, {"value": 1000} ],
}

const max = Math.max(...[].concat(...Object.values(d)).map(({value}) => value))
console.log(max)

answered Jun 18, 2019 at 7:56

Nenad Vracar

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Comments

Jack Bashford · Accepted Answer · 2019-06-18 08:00:31Z

2

Use Object.values, flatMap and Math.max with spreading.

const d = {"A":[{"value":10},{"value":20},{"value":30}],"B":[{"value":50},{"value":60},{"value":1000}]};
const res = Math.max(...Object.values(d).flat().flatMap(Object.values));
console.log(res);

Because flat isn't well supported (and neither is flatMap) you can use reduce as well.

const d = {"A":[{"value":10},{"value":20},{"value":30}],"B":[{"value":50},{"value":60},{"value":1000}]};
const res = Math.max(...Object.values(d).map(e => e.map(Object.values)).reduce((a, c) => [].concat(...a, ...c)));
console.log(res);

edited Jun 18, 2019 at 8:00

answered Jun 18, 2019 at 7:56

Jack Bashford

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5 Comments

Cid Over a year ago

Object.values(...).flat is not a function

Jack Bashford Over a year ago

It's running perfectly in the snippet @Cid - check your browser (flat isn't well-supported). I'll add some better-supported variants.

Cid Over a year ago

I'm using Firefox Quantum 60.7.0esr (32 bits)

Jack Bashford Over a year ago

I'm using Safari latest. Works perfectly.

Cid Over a year ago

Considering official browser compatibility it's available on firefox since the version 62

Pinetree · Accepted Answer · 2019-06-18 08:03:11Z

0

If you want es5 code, try this:

var d = {
"A": [ {"value": 10}, {"value": 20}, {"value": 30} ],
"B": [ {"value": 50}, {"value": 60}, {"value": 1000} ],
};

var results = [];
for(var key in d)
{
    d[key].forEach(function (obj){
        results.push(obj.value);
    });
}
console.log(Math.max.apply(null, results));

answered Jun 18, 2019 at 8:03

Pinetree

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Comments

Kunal Mukherjee · Accepted Answer · 2019-06-18 08:07:17Z

0

Try something like this by flattening the values first then sorting it in ascending order and taking the last element out of the sorted array:

const data = {
		"A": [ {"value": 10}, {"value": 20}, {"value": 30 } ],
		"B": [ {"value": 50}, {"value": 60}, {"value": 1000} ],
};


const highestValue = Object.values(data)
.flatMap(x => x)
.sort((a, b) => a.value - b.value)
.slice(-1);

console.log(highestValue);

answered Jun 18, 2019 at 8:07

Kunal Mukherjee

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Comments

Ziv Ben-Or · Accepted Answer · 2019-06-18 08:07:24Z

0

d = {
    "A": [{ "value": 10 }, { "value": 20 }, { "value": 30 }],
    "B": [{ "value": 50 }, { "value": 60 }, { "value": 1000 }],
}


var maxValue = Math.max.apply(null,Object.keys(d).map(key => Math.max.apply(null,d[key].map(x => x.value))));

console.log(maxValue);

answered Jun 18, 2019 at 8:07

Ziv Ben-Or

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Comments

Cid · Accepted Answer · 2019-06-18 08:09:35Z

0

You can use a good old loop

let d = {
"A": [ {"value": 10}, {"value": 20}, {"value": 30} ],
"B": [ {"value": 50}, {"value": 60}, {"value": 1000} ],
}

let maxValue;
for (let key in d)
{
  for (let i = 0, len = d[key].length; i < len; ++i)
  {
    if (maxValue === undefined || maxValue < d[key][i].value)
      maxValue = d[key][i].value;
  }
}

console.log(maxValue);

answered Jun 18, 2019 at 8:09

Cid

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Comments

Akrion · Accepted Answer · 2019-06-18 08:43:35Z

0

Since neither Array.flat nor Array.flatMap are well supported without polyfill here is a solution with Array.reduce, Object.values and Array.map:

const d = {
"A": [ {"value": 10}, {"value": 20}, {"value": 30} ],
"B": [ {"value": 50}, {"value": 60}, {"value": 1000} ],
}

let r = Math.max(...Object.values(d).reduce((r,c)=>[...r,...c]).map(x => x.value))

console.log(r)

The idea is to use Object.values to get straight to the values of the object. Then use Array.reduce for the flattening of the arrays and Array.map to extract the value. Then spread to Math.max for the final result.

answered Jun 18, 2019 at 8:43

Akrion

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Comments

shikhar · Accepted Answer · 2019-06-18 10:00:29Z

0

Only simply using map and reduce and chaining them together can give you the desired max value. I have used underscore js though, you can use simple map and reduce methods for the same.

var d = {
     "A": [ {"value": 10}, {"value": 20}, {"value": 30} ],
     "B": [ {"value": 50}, {"value": 60}, {"value": 1000} ],
     "C": [ {"value": 30}, {"value": 90}, {"value": 300} ],
     }

var maxvalue = _.reduce(_.map(d,(items)=>{  
    return _.reduce(items , (p,i)=>{
            return p> i.value ? p: i.value;
        },0)
}) , (maxy, iter)=>{
    return maxy > iter ? maxy: iter;
},0);

answered Jun 18, 2019 at 10:00

shikhar

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Comments

Slai · Accepted Answer · 2019-06-18 11:56:10Z

0

For actual JSON string, it can be done during parsing :

var max = -Infinity, json = '{"A":[{"value":10},{"value":20},{"value":30}],"B":[{"value":50},{"value":60},{"value":1000}]}'

JSON.parse(json, (k, v) => max = v > max ? v : max)

console.log( max )

For JavaScript object :

const d = { "A": [ {"value": 10}, {"value": 20}, {"value":   30 } ],
            "B": [ {"value": 50}, {"value": 60}, {"value": 1000 } ] }

console.log( Math.max(...Object.values(d).flat().map(x => x.value)) )

edited Jun 18, 2019 at 11:56

answered Jun 18, 2019 at 9:53

Slai

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